Changeset 781 for trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt/config.py

Timestamp:

Jul 29, 2008, 10:35:08 PM (16 years ago)

Author:

y_z

Message:

• added file locking around cache
• cleanup

File:

• trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt/config.py (modified) (2 diffs)

trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt/config.py

@@ -1 +1 @@
 import json, yaml
 from invirt.common import *
-from os import error, makedirs
-from os.path import dirname, getmtime
+from os.path import getmtime
 
 default_src_path   = '/etc/invirt/master.yaml'
-default_cache_path = '/var/lib/invirt/invirt.json'
+default_cache_path = '/var/lib/invirt/cache.json'
 
 try:    default_loader = yaml.CSafeLoader
@@ -29 +28 @@
     if not do_refresh:
         # try reading from the cache first
-        try: cfg = wrap(file(cache_path), lambda f: json.read(f.read()))
+        try: cfg = with_closing(file(cache_path))(lambda f: json.read(f.read()))
         except: do_refresh = True
 
     if do_refresh:
-        # reload the source and regenerate the cache
-        cfg = wrap(file(src_path), lambda f: yaml.load(f, default_loader))
-        try: wrap(file(cache_path, 'w'), lambda f: f.write(json.write(cfg)))
-        except: pass # silent failure
+        # Atomically reload the source and regenerate the cache.  The read and
+        # write must be a single transaction, or a stale version may be
+        # written.
+        @with_lock_file('/var/lib/invirt/cache.lock')
+        def cfg():
+            cfg = with_closing(file(src_path))(lambda f: yaml.load(f, default_loader))
+            try: with_closing(file(cache_path, 'w'))(lambda f: f.write(json.write(cfg)))
+            except: pass # silent failure
+            return cfg
     return cfg